1. Field of the Invention
The present invention generally relates to a dental attachment, a dental keeper, a dental magnet and a method for taking an impression using thereof, and more particularly, to a dental attachment used for dental prostheses such as a denture, a crown and a crown-and-bridge set, and a dental keeper of the dental attachment which use magnetic force for retention and a method for taking an impression using thereof.
2. Description of the Related Art
Various methods have been used for retaining a dental prosthesis such as a denture, a crown and a crown-and-bridge set in medicine and dentistry. For instance, methods which use a mechanical attachment used to be among the main methods for the purpose. These days, however, a magnetic attachment (also called as a magnetic retention, a magnetic system, a magnetic anchor attachment, rare earth attachment and so on) utilizing a potent magnet of small size has been developed and applied clinically.
In general, a magnetic attachment is comprised of a magnetic assembly, which is provided with a dental prosthesis, and a dental keeper made of a steel plate (usually a stainless steel plate), which may be attached to an abutment. Thus, the dental keeper is attracted to the magnetic assembly by the magnetic force and the denture prosthesis is attached to the abutment.
FIG. 1 is a diagram for explaining an example of a conventional dental prosthesis (denture) using a magnetic attachment. The dental prosthesis 155 includes a denture portion comprising a magnet 152, a resin base 156 and an artificial tooth 157, and a dental keeper 151 formed integrally with a root cap 153. The numeral 158 indicates gingival tissues and the numeral 159 indicates a root of a tooth. The dental keeper 151, which is made of a magnetic stainless steel (or magnetic metal), is embedded in the upper portion of the root cap 153 so that the denture portion is fixed to the root cap 153 through the magnetic force of the magnet 152.
The above-mentioned magnetic attachment has advantages in that an excessive stress on the abutments at the time of insertion and removal of a dental prosthesis may be eliminated, unlike the mechanical attachments, and the insertion/removal operation of the dental prosthesis itself is very easy. Also, the degree of the holding force of the magnet used may be measured and it is not attenuated during a long-term use. Moreover, the magnetic attachments are non-directional for the insertion and removal of dental prostheses and they transmit little lateral force to the abutments.
However, when the magnetic assembly and the dental keeper are positioned at their respective locations manually, it is difficult to exactly position them at a desired location, and it requires a skillful hand for carrying out the operation. Also, since the dental keeper is embedded in the upper portion of the root cap, it is difficult to adjust the position of the dental keeper when a shift in location of the dental keeper has occurred. Moreover, there have been reports of accidents in which dental prostheses were faultily detached due to an instable attachment of the dental keeper and the magnetic assembly.
On the other hand, it has been proposed to make the dental keeper of a magnetic attachment removable since there is a danger that the magnetic attachment has an effect on biological measurements which utilize a magnetic force such as MRI. However, the proposed method is a method in which the dental keeper is embedded completely in the root cap. Therefore, according to the above method, the size of the dental keeper must be reduced since there is additional space needed for a metal part which is used for covering the dental keeper. Hence, it is likely that the operation according to the above method becomes tedious and complicated.